Plasma spray coating enhancement using plasma flame heat treatment

ABSTRACT

A method for forming a plasma resistant ceramic coating on an article includes placing the article into a chamber or spray cell of a plasma spraying system. A ceramic powder is then fed into the plasma spraying system at a powder feed rate, and a plasma resistant ceramic coating is deposited onto at least one surface of the article in a plasma spray process by the plasma spray system. The plasma spray system is then used to perform an in-situ plasma flame heat treatment of the plasma resistant ceramic coating to form crust on the plasma resistant ceramic coating.

RELATED APPLICATIONS

This patent application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Application No. 61/879,549, filed Sep. 18, 2013.

TECHNICAL FIELD

Embodiments of the present disclosure relate, in general, to ceramiccoated articles and to a process for plasma spraying a ceramic coatingonto chamber components.

BACKGROUND

In the semiconductor industry, devices are fabricated by a number ofmanufacturing processes producing structures of an ever-decreasing size.Some manufacturing processes such as plasma etch and plasma cleanprocesses expose a substrate to a high-speed stream of plasma to etch orclean the substrate. The plasma may be highly corrosive, and may corrodeprocessing chambers and other surfaces that are exposed to the plasma.This corrosion may generate particles, which frequently contaminate thesubstrate that is being processed, contributing to device defects.

As device geometries shrink, susceptibility to defects increases andparticle contaminant requirements become more stringent. Accordingly, asdevice geometries shrink, allowable levels of particle contamination maybe reduced. To minimize particle contamination introduced by plasma etchand/or plasma clean processes, chamber materials have been developedthat are resistant to plasmas. Different materials provide differentmaterial properties, such as plasma resistance, rigidity, flexuralstrength, thermal shock resistance, and so on. Also, different materialshave different material costs. Accordingly, some materials have superiorplasma resistance, other materials have lower costs, and still othermaterials have superior flexural strength and/or thermal shockresistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 depicts a sectional view of one embodiment of a processingchamber.

FIG. 2 illustrates an exemplary architecture of a manufacturing system,in accordance with one embodiment of the present invention.

FIGS. 3-4 depict schematics of a plasma spray deposition system.

FIG. 5 illustrates one embodiment of a process for forming a plasmasprayed ceramic coating over a chamber component.

FIG. 6 illustrates a cross sectional side view of an article covered bya plasma sprayed protective layer having a crust formed by a plasmaflame heat treatment process.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the disclosure are directed to a process for coating anarticle with a ceramic coating and to performing a plasma flame heattreatment on the ceramic coating. The processes disclosed herein provideimproved plasma resistance performance for chamber components withreduced processing time and lower cost than conventional plasmaresistant coatings.

In one embodiment, an article is positioned with reference to a plasmaspraying system. Ceramic powder is fed into the plasma spraying systemat a powder feed rate, and the plasma spraying system deposits a plasmaresistant ceramic coating on at least one surface of the article in aplasma spray process. The plasma spray system then performs an in-situplasma flame heat treatment of the plasma resistant ceramic coating toform a crust on the plasma resistant ceramic coating. In some instances,the plasma flame heat treatment is superior to laser melting, sparkplasma sintering and furnace heat treatments. Each of these other heattreatments are performed by equipment other than the plasma spray systemused to deposit the plasma resistant ceramic coating. Accordingly, alead time is increased for these other heat treatment processes.Additionally, transport of the article to the equipment for the otherheat treatment processes increases a risk of contamination. In addition,laser melting may create vertical and horizontal cracks in the ceramiccoating. Spark plasma sintering is limited in application to smallsample sizes. Furnace heat treatment is not applicable for many types ofsubstrates, such as for some metal substrates, electrostatic chucks, andso on.

By heat treating the plasma sprayed ceramic coating using the plasmaflame heat treatment, a surface of the coating is reflowed to form acrust at the surface having reduced porosity and cracks. Theheat-treated ceramic coating of the article may be highly resistant toplasma etching, and the article may have superior mechanical propertiessuch as a high flexural strength and a high hardness. Performanceproperties of the coated ceramic article may include a high thermalcapability, a long lifespan, and a low on-wafer particle and metalcontamination.

When the terms “about” and “approximately” are used herein, these areintended to mean that the nominal value presented is precise within±30%. The articles described herein may be structures that are exposedto plasma, such as chamber components for a plasma etcher (also known asa plasma etch reactor). For example, the articles may be walls, bases,gas distribution plates, shower heads, substrate holding frames,electrostatic chucks, rings, lids, nozzles, faceplates, selectivitymodulation devices (SMDs) etc. of a plasma etcher, a plasma cleaner, aplasma propulsion system, and so forth.

Moreover, embodiments are described herein with reference to ceramiccoated chamber components and other articles that may cause reducedparticle contamination when used in a process chamber for plasma richprocesses. However, it should be understood that the ceramic coatedarticles discussed herein may also provide reduced particlecontamination when used in process chambers for other processes such asnon-plasma etchers, non-plasma cleaners, chemical vapor deposition (CVD)chamber, physical vapor deposition (PVD) chamber, and so forth.Moreover, some embodiments are described with reference to specificplasma resistant ceramics. However, it should be understood thatembodiments equally apply to other plasma resistant ceramics than thosediscussed herein.

FIG. 1 is a sectional view of a processing chamber 100 (e.g., asemiconductor processing chamber) having one or more chamber componentsthat are coated with a ceramic coating in accordance with embodiments ofthe present invention. The ceramic coating described in embodiments is aplasma-sprayed coating that has been heat treated using a plasma flameheat treatment by a torch of a plasma spraying system. The processingchamber 100 may be used for processes in which a corrosive plasmaenvironment is provided. For example, the processing chamber 100 may bea chamber for a plasma etch reactor (also known as a plasma etcher), aplasma cleaner, and so forth. Examples of chamber components that mayinclude a plasma resistant ceramic coating include a substrate supportassembly 148, an electrostatic chuck (ESC) 150, a ring (e.g., a processkit ring or single ring), a chamber wall, a base, a gas distributionplate, a showerhead, a liner, a liner kit, a shield, a plasma screen, aflow equalizer, a cooling base, a chamber viewport, a chamber lid, anozzle, process kit rings, a faceplate, an SMD, and so on.

The plasma resistant ceramic coating, which is described in greaterdetail below, is a rare earth oxide coating deposited by an atmosphericpressure plasma spraying (APPS) process. The plasma resistant ceramiccoating may have a crust that has been formed by a plasma flame heattreatment process, in accordance with embodiments. The plasma resistantcoating may include Y₂O₃ and Y₂O₃ based ceramics, Y₃Al₅O₁₂ (YAG), Al₂O₃(alumina), Y₄Al₂O₉ (YAM), SiC (silicon carbide) Si₃N₄ (silicon nitride),SiN (silicon nitride), AlN (aluminum nitride), TiO₂ (titania), ZrO₂(zirconia), TiC (titanium carbide), ZrC (zirconium carbide), TiN(titanium nitride), Y₂O₃ stabilized ZrO₂ (YSZ), Er₂O₃ and Er₂O₃ basedceramics, Gd₂O₃ and Gd₂O₃ based ceramics, Er₃Al₅O₁₂ (EAG), Gd₃Al₅O₁₂(GAG), Nd₂O₃ and Nd₂O₃ based ceramics, and/or a ceramic compoundcomprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.

The plasma resistant coating may also be based on a solid solutionformed by any of the aforementioned ceramics. With reference to theceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂,in one embodiment the ceramic compound includes 62.93 molar ratio (mol%) Y₂O₃, 23.23 mol % ZrO₂ and 13.94 mol % Al₂O₃. In another embodiment,the ceramic compound can include Y₂O₃ in a range of 50-75 mol %, ZrO₂ ina range of 10-30 mol % and Al₂O₃ in a range of 10-30 mol %. In anotherembodiment, the ceramic compound can include Y₂O₃ in a range of 40-100mol %, ZrO₂ in a range of 0-60 mol % and Al₂O₃ in a range of 0-10 mol %.In another embodiment, the ceramic compound can include Y₂O₃ in a rangeof 40-60 mol %, ZrO₂ in a range of 30-50 mol % and Al₂O₃ in a range of10-20 mol %. In another embodiment, the ceramic compound can includeY₂O₃ in a range of 40-50 mol %, ZrO₂ in a range of 20-40 mol % and Al₂O₃in a range of 20-40 mol %. In another embodiment, the ceramic compoundcan include Y₂O₃ in a range of 70-90 mol %, ZrO₂ in a range of 0-20 mol% and Al₂O₃ in a range of 10-20 mol %. In another embodiment, theceramic compound can include Y₂O₃ in a range of 60-80 mol %, ZrO₂ in arange of 0-10 mol % and Al₂O₃ in a range of 20-40 mol %. In anotherembodiment, the ceramic compound can include Y₂O₃ in a range of 40-60mol %, ZrO₂ in a range of 0-20 mol % and Al₂O₃ in a range of 30-40 mol%. In other embodiments, other distributions may also be used for theceramic compound.

In one embodiment, an alternative ceramic compound that includes acombination of Y₂O₃, ZrO₂, Er₂O₃, Gd₂O₃ and SiO₂ is used for theprotective layer. In one embodiment, the alternative ceramic compoundcan include Y₂O₃ in a range of 40-45 mol %, ZrO₂ in a range of 0-10 mol%, Er2O3 in a range of 35-40 mol %, Gd₂O₃ in a range of 5-10 mol % andSiO2 in a range of 5-15 mol %. In a first example, the alternativeceramic compound includes 40 mol % Y₂O₃, 5 mol % ZrO₂, 35 mol % Er₂O₃, 5mol % Gd₂O₃ and 15 mol % SiO₂. In a second example, the alternativeceramic compound includes 45 mol % Y₂O₃, 5 mol % ZrO₂, 35 mol % Er₂O₃,10 mol % Gd₂O₃ and 5 mol % SiO₂. In a third example, the alternativeceramic compound includes 40 mol % Y₂O₃, 5 mol % ZrO₂, 40 mol % Er₂O₃, 7mol % Gd₂O₃ and 8 mol % SiO₂.

Any of the aforementioned plasma resistant ceramic coatings may includetrace amounts of other materials such as ZrO₂, Al₂O₃, SiO₂, B₂O₃, Er₂O₃,Nd₂O₃, Nb₂O₅, CeO₂, Sm₂O₃, Yb₂O₃, or other oxides. The ceramic coatingallows for longer working lifetimes due to the plasma resistance of theceramic coating and decreased on-wafer or substrate contamination.Beneficially, in some embodiments the ceramic coating may be strippedand re-coated without affecting the dimensions of the substrates thatare coated.

In one embodiment, the processing chamber 100 includes a chamber body102 and a lid 130 that enclose an interior volume 106. The lid 130 mayhave a hole in its center, and a nozzle 132 may be inserted into thehole. The chamber body 102 may be fabricated from aluminum, stainlesssteel or other suitable material. The chamber body 102 generallyincludes sidewalls 108 and a bottom 110. Sidewalls 108 and/or bottom 110may include a plasma resistant ceramic coating.

An outer liner 116 may be disposed adjacent the sidewalls 108 to protectthe chamber body 102. The outer liner 116 may be fabricated and/orcoated with a plasma resistant ceramic coating. In one embodiment, theouter liner 116 is fabricated from aluminum oxide.

An exhaust port 126 may be defined in the chamber body 102, and maycouple the interior volume 106 to a pump system 128. The pump system 128may include one or more pumps and throttle valves utilized to evacuateand regulate the pressure of the interior volume 106 of the processingchamber 100.

The lid 130 may be supported on the sidewall 108 of the chamber body102. The lid 130 may be opened to allow access to the interior volume106 of the processing chamber 100, and may provide a seal for theprocessing chamber 100 while closed. A gas panel 158 may be coupled tothe processing chamber 100 to provide process and/or cleaning gases tothe interior volume 106 through the nozzle 132. The lid 130 may be aceramic such as Al₂O₃, Y₂O₃, YAG, SiO₂, MN, SiN, SiC, Si—SiC, or aceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.The nozzle 132 may also be a ceramic, such as any of those ceramicsmentioned for the lid. The lid 130 may include a plasma resistantceramic coating 133. The nozzle 132 may be coated with a plasmaresistant ceramic coating 134.

Examples of processing gases that may be used to process substrates inthe processing chamber 100 include halogen-containing gases, such asC₂F₆, SF₆, SiCl₄, HBr, NF₃, CF₄, CHF₃, CH₂F₃, F, NF₃, Cl₂, CCl₄, BCl₃and SiF₄, among others, and other gases such as O₂, or N₂O. Examples ofcarrier gases include N₂, He, Ar, and other gases inert to process gases(e.g., non-reactive gases). A substrate support assembly 148 is disposedin the interior volume 106 of the processing chamber 100 below the lid130. The substrate support assembly 148 holds a substrate 144 duringprocessing. A ring 146 (e.g., a single ring) may cover a portion of theelectrostatic chuck 150, and may protect the covered portion fromexposure to plasma during processing. The ring 146 may be silicon orquartz in one embodiment. The ring 146 may include a plasma resistantceramic coating.

An inner liner 118 may be coated on the periphery of the substratesupport assembly 148. The inner liner 118 may be a halogen-containinggas resist material such as those discussed with reference to the outerliner 116. In one embodiment, the inner liner 118 may be fabricated fromthe same materials of the outer liner 116. Additionally, the inner liner118 may be coated with a plasma resistant ceramic coating.

In one embodiment, the substrate support assembly 148 includes amounting plate 162 supporting a pedestal 152, and an electrostatic chuck150. The electrostatic chuck 150 further includes a thermally conductivebase 164 and an electrostatic puck 166 bonded to the thermallyconductive base by a bond 138, which may be a silicone bond in oneembodiment. The mounting plate 162 is coupled to the bottom 110 of thechamber body 102 and includes passages for routing utilities (e.g.,fluids, power lines, sensor leads, etc.) to the thermally conductivebase 164 and the electrostatic puck 166.

The electrostatic puck 166 may include a plasma resistant ceramiccoating. The thermally conductive base 164 and/or electrostatic puck 166may include one or more optional embedded heating elements 176, embeddedthermal isolators 174 and/or conduits 168, 170 to control a lateraltemperature profile of the substrate support assembly 148. The conduits168, 170 may be fluidly coupled to a fluid source 172 that circulates atemperature regulating fluid through the conduits 168, 170. The embeddedthermal isolators 174 may be disposed between the conduits 168, 170 inone embodiment. The heating elements 176 are regulated by a heater powersource 178. The conduits 168, 170 and heating elements 176 may beutilized to control the temperature of the thermally conductive base164, thereby heating and/or cooling the electrostatic puck 166 and asubstrate (e.g., a wafer) 144 being processed. The temperature of theelectrostatic puck 166 and the thermally conductive base 164 may bemonitored using a plurality of temperature sensors 190, 192, which maybe monitored using a controller 195.

The electrostatic puck 166 may further include multiple gas passagessuch as grooves, mesas and other surface features that may be formed inan upper surface of the puck 166. The gas passages may be fluidlycoupled to a source of a heat transfer (or backside) gas such as He viaholes drilled in the puck 166. In operation, the backside gas may beprovided at controlled pressure into the gas passages to enhance theheat transfer between the electrostatic puck 166 and the substrate 144.

The electrostatic puck 166 includes at least one clamping electrode 180controlled by a chucking power source 182. The at least one clampingelectrode 180 (or other electrode disposed in the electrostatic puck 166or thermally conductive base 164) may further be coupled to one or moreRF power sources 184, 186 through a matching circuit 188 for maintaininga plasma formed from process and/or other gases within the processingchamber 100. The RF power sources 184, 186 are generally capable ofproducing RF signal having a frequency from about 50 kHz to about 3 GHzand a power of up to about 10,000 Watts.

FIG. 2 illustrates an exemplary architecture of a manufacturing system200. The manufacturing system 200 may be a ceramics manufacturingsystem. In one embodiment, the manufacturing system 200 includesmanufacturing machines 201 (also referred to as processing equipment)connected to an equipment automation layer 215. The manufacturingmachines 201 may include a bead blaster 202, one or more wet cleaners203, and/or a plasma spraying system 204. The manufacturing system 200may further include one or more computing device 220 connected to theequipment automation layer 215. In alternative embodiments, themanufacturing system 200 may include more or fewer components. Forexample, the manufacturing system 200 may include manually operated(e.g., off-line) manufacturing machines 201 without the equipmentautomation layer 215 or the computing device 220.

Bead blaster 202 is a machine configured to roughen the surface ofarticles such as articles. Bead blaster 202 may be a bead blastingcabinet, a hand held bead blaster, or other type of bead blaster. Beadblaster 202 may roughen a substrate by bombarding the substrate withbeads or particles. In one embodiment, bead blaster 202 fires ceramicbeads or particles at the substrate. The roughness achieved by the beadblaster 202 may be based on a force used to fire the beads, beadmaterials, bead sizes, distance of the bead blaster from the substrate,processing duration, and so forth. In one embodiment, the bead blasteruses a range of bead sizes to roughen the ceramic article.

In alternative embodiments, other types of surface rougheners than abead blaster 202 may be used. For example, a motorized abrasive pad maybe used to roughen the surface of ceramic substrates. A sander mayrotate or vibrate the abrasive pad while the abrasive pad is pressedagainst a surface of the article. A roughness achieved by the abrasivepad may depend on an applied pressure, on a vibration or rotation rateand/or on a roughness of the abrasive pad.

Wet cleaners 203 are cleaning apparatuses that clean articles (e.g.,articles) using a wet clean process. Wet cleaners 203 include wet bathsfilled with liquids, in which the substrate is immersed to clean thesubstrate. Wet cleaners 203 may agitate the wet bath using ultrasonicwaves during cleaning to improve a cleaning efficacy. This is referredto herein as sonicating the wet bath.

In other embodiments, alternative types of cleaners such as dry cleanersmay be used to clean the articles. Dry cleaners may clean articles byapplying heat, by applying gas, by applying plasma, and so forth.

Plasma spraying system 204 is a machine configured to plasma spray aceramic coating to the surface of a substrate. In one embodiment, plasmaspraying system 204 is an atmospheric pressure plasma spraying (APPS)system (also referred to as an air plasma spraying (APS) system). Plasmaspraying systems are discussed in greater detail with reference to FIGS.3-4.

The equipment automation layer 215 may interconnect some or all of themanufacturing machines 201 with computing devices 220, with othermanufacturing machines, with metrology tools and/or other devices. Theequipment automation layer 215 may include a network (e.g., a locationarea network (LAN)), routers, gateways, servers, data stores, and so on.Manufacturing machines 201 may connect to the equipment automation layer215 via a SEMI Equipment Communications Standard/Generic Equipment Model(SECS/GEM) interface, via an Ethernet interface, and/or via otherinterfaces. In one embodiment, the equipment automation layer 215enables process data (e.g., data collected by manufacturing machines 201during a process run) to be stored in a data store (not shown). In analternative embodiment, the computing device 220 connects directly toone or more of the manufacturing machines 201.

In one embodiment, some or all manufacturing machines 201 include aprogrammable controller that can load, store and execute processrecipes. The programmable controller may control temperature settings,gas and/or vacuum settings, time settings, etc. of manufacturingmachines 201. The programmable controller may include a main memory(e.g., read-only memory (ROM), flash memory, dynamic random accessmemory (DRAM), static random access memory (SRAM), etc.), and/or asecondary memory (e.g., a data storage device such as a disk drive). Themain memory and/or secondary memory may store instructions forperforming heat treatment processes described herein.

The programmable controller may also include a processing device coupledto the main memory and/or secondary memory (e.g., via a bus) to executethe instructions. The processing device may be a general-purposeprocessing device such as a microprocessor, central processing unit, orthe like. The processing device may also be a special-purpose processingdevice such as an application specific integrated circuit (ASIC), afield programmable gate array (FPGA), a digital signal processor (DSP),network processor, or the like. In one embodiment, programmablecontroller is a programmable logic controller (PLC).

In one embodiment, the manufacturing machines 201 are programmed toexecute recipes that will cause the manufacturing machines to roughen asubstrate, clean a substrate and/or article, coat a article and/ormachine (e.g., grind or polish) a article. In one embodiment, themanufacturing machines 201 are programmed to execute recipes thatperform operations of a multi-step process for manufacturing a ceramiccoated article, as described with reference to FIG. 5. The computingdevice 220 may store one or more ceramic coating recipes 225 that can bedownloaded to the manufacturing machines 201 to cause the manufacturingmachines 201 to manufacture ceramic coated articles in accordance withembodiments of the present disclosure.

FIGS. 3-4 illustrate a plasma spray system 300 for plasma spraying aplasma resistant ceramic coating on a chamber component, or otherarticle used in a corrosive system. The plasma spray system 300 is atype of thermal spray system. In a plasma spray system, an arc is formedbetween two electrodes through which a gas is flowing. Examples of gassuitable for use in the plasma spray system 300 include, but are notlimited to, Argon/Hydrogen or Argon/Helium. As the gas is heated by thearc, the gas expands and is accelerated through a shaped nozzle of aplasma torch 304, creating a high velocity plasma jet 302.

Powder 309 is injected into the plasma jet 302 by a powder deliverysystem 308. An intense temperature of the plasma jet 302 melts thepowder 309 and propels the molten ceramic material towards an article310. Upon impacting with the article 310, the molten powder flattens,rapidly solidifies, and forms a ceramic coating 312. The molten powderadheres to the article 310. The parameters that affect the thickness,density, and roughness of the ceramic coating 312 include type ofpowder, powder size distribution, powder feed rate, plasma gascomposition, gas flow rate, energy input, pressure, and torch offsetdistance.

In one embodiment, the plasma spray system 300 is a conventionalatmospheric pressure plasma spray (APPS) system that operates atatmospheric pressure to perform an APPS process. An APPS system does notinclude any vacuum chamber, and may instead include an open chamber orroom. APPS systems produce oxide ceramic coatings having a relativelyhigh porosity. For example, APPS systems may produce ceramic coatingswith a porosity of 1-5% in some embodiments. An APPS system may produceceramic coatings having thicknesses of around 20 microns to severalmillimeters. For APPS, the ceramic coating bonds to the substrate mainlyby mechanical bonding. Accordingly, in one embodiment the article 310 isroughened prior to forming the plasma sprayed ceramic coating 312.

In one embodiment, after the ceramic coating 312 is formed, the powderdelivery system 308 may stop feeding ceramic powder into the plasma jet302, as shown in FIG. 4. One or more of the plasma gas composition, gasflow rate, energy input, or torch offset distance may additionally beadjusted at this point. Values used for these parameters in someembodiments are represented below in Table 1. The plasma jet 302 maythen be used to perform a plasma flame heat treatment of the ceramiccoating 312. This plasma flame heat treatment may melt and reflow asurface of the ceramic coating to form a thin crust on the surface ofthe ceramic coating 312. The thin crust may have a reduced surfaceroughness, an increased density, and a reduced porosity. A thickness ofthe crust may be around 1 micron up to about 40 or 50 microns. In oneembodiment, the crust has a thickness of about 20-40 microns.Additionally, the plasma flame heat treatment may reduce or eliminatesome of all surface cracks of the ceramic coating. This plasma flameheat treatment may also reduce or eliminate loosely bonded particles onthe surface of the ceramic coating, and may reduce or eliminate noduleson the surface of the ceramic coating.

FIG. 5 illustrates one embodiment of a process 500 for forming a plasmasprayed ceramic coating over a chamber component. At block 501, asubstrate is prepared for coating. The substrate may be a metalsubstrate such as aluminum, copper, magnesium, or another metal or ametal alloy. The substrate may also be a ceramic substrate, such asalumina, yttria, or another ceramic or a mixture of ceramics. Preparingthe substrate may include shaping the substrate to a desired form,grinding, blasting or roughening the substrate to provide a particularsurface roughness and/or cleaning the substrate. In one embodiment, thesubstrate is roughened. This may activate the surface by increasing thefree space energy and may strengthen mechanical bonding of the ceramiccoating to the substrate.

At block 502, optimal powder characteristics for plasma spraying aceramic coating are selected. In one embodiment, an optimal powder typeand an optimal powder size distribution are selected for the powder. Inone embodiment, an optimized agglomerate powder size distribution isselected where 10% of agglomerate powder (D10) has a size of less than10 μm, 50% of agglomerate powder (D50) has a size of 10-30 μm and 90% ofagglomerate powder (D90) has a size of less than 55 μm.

Raw ceramic powders having specified compositions, purity and particlesizes are selected. The ceramic powder may be formed of any of the rareearth oxides previously discussed. The raw ceramic powders are thenmixed. These raw ceramic powders may have a purity of 99.9% or greaterin one embodiment. The raw ceramic powders may be mixed using, forexample, ball milling. The raw ceramic powders may have a powder size ofin the range of between about 100 nm-20 μm. In one embodiment, the rawceramic powders have a powder size of approximately 5 μm.

After the ceramic powders are mixed, they may be calcinated at aspecified calcination time and temperature. In one embodiment, acalcination temperature of approximately 1200-2000° C. (e.g., 1400° C.in one embodiment) and a calcination time of approximately 2-5 hours(e.g., 3 hours in one embodiment) is used. The spray dried granularparticle size for the mixed powder may have a size distribution ofapproximately 30 μm in one embodiment.

At block 504, optimal plasma spray parameters are selected. In oneembodiment, optimizing plasma spray parameters includes, but is notlimited to, setting a plasma gun power and a composition of spraycarrier gas.

Optimizing the powder characteristics and the plasma spray parametersmay lead to a coating with a decreased porosity and an increaseddensity. Such a decreased porosity and increased density improvesprotection of a coated article from corrosive elements such as plasmas.Also, fully melted nodules are less likely to break free of the ceramiccoating and contaminate the substrate or wafer causing particleproblems.

At block 506, the article is coated according to the selected powdercharacteristics and plasma spray parameters. Plasma spraying techniquesmay melt materials (e.g., ceramic powders) and spray the meltedmaterials onto the article using the selected parameters. In oneembodiment, the plasma sprayed ceramic coating may have a thicknessabout 200-650 microns.

The plasma spray process may be performed in multiple spray passes. Foreach pass, the angle of a plasma spray nozzle may change to maintain arelative angle to a surface that is being sprayed. For example, theplasma spray nozzle may be rotated to maintain an angle of approximately45 degrees to approximately 90 degrees with the surface of the articlebeing sprayed. Each pass may deposit a thickness of up to approximately25 μm. The plasma sprayed plasma resistant ceramic coating may have asurface roughness of about 160-300 micro-inches.

At block 508, the plasma spray parameters are adjusted and a powder feedrate is reduced to zero. Accordingly, at block 508 the flow of powderinto the plasma jet is stopped. The changes to the plasma sprayparameters may include changing a plasma power, a torch offset distance,a gun moving speed, and so on.

TABLE 1 Plasma Spray Input Parameters Heat Coating Treatment InputParameter Unit Range Range Power of Plasma kW  9-300 35-300 Gun CurrentA 300-1000 500-1000 Gun Voltage V 30-300 70-300 Powder Feed g/min. 5-200 0 Distance mm 50-200 20-100 Gas Flow Rate L/min. 30-500 50-500

Table 1 illustrates input parameter ranges that may be used for coatingthe article and for performing a plasma flame heat treatment to form acrust on the coating. The parameters include, but are not limited to,power of plasma, gun current, gun voltage, powder feed rate, gunstand-off distance, and gas flow rate.

At block 510, the plasma spray system is used to perform a plasma flameheat treatment on the plasma resistant ceramic coating according to theadjusted plasma spray parameters. The plasma flame heat treatment may beperformed for about 0.5-20 minutes in one embodiment. The plasma flameheat treatment may be performed for about 10-15 minutes in anotherembodiment. The plasma flame heat treatment may cause a surface of theplasma resistant ceramic coating to melt and reflow, which causes acrust to form on a surface of the plasma resistant ceramic coating. Thismay reduce or eliminate loose particles on the ceramic coating, and mayreduce or eliminate partially melted nodules. Both unmelted particlesand partially melted nodules can cause contamination during processing.Additionally, the crust may have a higher density and lower porositythan the rest of the plasma resistant ceramic layer. In one embodiment,the crust has a thickness of between about 1 micron and about 40microns. In one embodiment, the crust has a thickness of less than 20microns. The crust may have a surface roughness that is approximately20-25% lower (smoother) than a surface roughness of the plasma resistantceramic coating prior to the plasma flame heat treatment. In anotherembodiment, the crust has a thickness of less than 1 micron. The crustmay have a surface roughness of about 100-150 micro-inches in oneembodiment.

TABLE 2 Plasma Spray Coating Range Optimized Metric Units RangePartially Melted Surface Nodules %  5%-20% Surface Roughness μ- 160-250inch HCI Bubble Time hr  >4 Breakdown Voltage V/mil >500

Table 2 illustrates measured coating characteristics using the optimizedplasma and powder parameters as described above.

FIG. 6 illustrates a cross sectional side view of an article (e.g.,chamber component) covered by plasma resistant ceramic coating having acrust that has been formed by a plasma flame heat treatment process. Abody 605 of the article 600 includes a plasma resistant ceramic coating608 having a crust 610 that has been formed by a plasma flame heattreatment process. The plasma resistant ceramic coating 608 may have aporosity and cracking. The crust formed by the plasma flame heattreatment may have a lower porosity and fewer cracks. Additionally, thecrust may have a lower surface roughness, reduced particles and fewersurface nodules as compared to a plasma resistant ceramic coating thathas not been heat treated. The plasma resistant ceramic coating 608 mayhave a thickness of about 100-500 μm and a porosity of about 1-5%. Thecrust 610 may have a thickness of about 1-50 microns.

Examples of ceramics that may be used to form the plasma resistantceramic coating 608 include Y₃Al₅O₁₂, Y₄Al₂O₉, Er₂O₃, Gd₂O₃, Er₃Al₅O₁₂,Gd₃Al₅O₁₂, a ceramic compound comprising Y₄Al₂O₉ and a solid-solution ofY₂O₃—ZrO₂, or any of the other ceramic materials previously identified.Other Er based and/or Gd based plasma resistant rare earth oxides mayalso be used to form the plasma resistant ceramic coating 608.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent disclosure. It will be apparent to one skilled in the art,however, that at least some embodiments of the present disclosure may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present disclosure. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentdisclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.”

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the disclosure should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A method, comprising: feeding a ceramic powderinto a plasma spraying system at a powder feed rate; depositing a plasmaresistant ceramic coating on at least one surface of an article in aplasma spray process by the plasma spray system; and performing anin-situ plasma flame heat treatment of the plasma resistant ceramiccoating by the plasma spray system to form a crust on the plasmaresistant ceramic coating.
 2. The method of claim 1, wherein performingthe in-situ plasma flame heat treatment comprises: adjusting at leastone of a plasma power, a gun moving speed or a gun distance of theplasma spraying system; and reducing the powder feed rate of the ceramicpowder to zero.
 3. The method of claim 1, wherein the article is achamber component for a plasma etch reactor, the article comprising atleast one of a metal or a sintered ceramic.
 4. The method of claim 1,wherein the plasma resistant ceramic coating comprises at least one ofY₃Al₅O₁₂, Y₄Al₂O₉, Er₂O₃, Gd₂O₃, Y₂O₃, Er₃Al₅O₁₂, Gd₃Al₅O₁₂, YF₃, orNd₂O₃.
 5. The method of claim 1, wherein the plasma resistant ceramiccoating comprises a ceramic compound comprising Y₄Al₂O₉ and asolid-solution of Y₂O₃—ZrO₂.
 6. The method of claim 1, wherein theplasma resistant ceramic coating has a porosity of 1-5%, and wherein thecrust has a lower porosity than the plasma resistant ceramic coating. 7.The method of claim 1, wherein the crust has a thickness of less thanabout 50 microns.
 8. The method of claim 1, wherein the crust has athickness of less than about 20 microns.
 9. The method of claim 1,wherein the in-situ plasma flame heat treatment is performed forapproximately 0.5-20 minutes.
 10. The method of claim 1, wherein thein-situ plasma flame heat treatment is performed for approximately 10-15minutes.
 11. The method of claim 1, wherein the plasma resistant ceramiccoating has a thickness of at least 100 microns.
 12. The method of claim1, wherein the plasma spraying system comprises an atmospheric plasmaspraying system.
 13. An article comprising: a body; a plasma resistantceramic coating on at least one surface of the body, the plasmaresistant ceramic coating having a porosity of 1-5%; and a crust on asurface of the plasma resistant ceramic coating, the crust having athickness of less than about 50 microns and a porosity that is lowerthan the porosity of the plasma resistant ceramic coating.
 14. Thearticle of claim 13, wherein the article is a chamber component for aplasma etch reactor, the article comprising at least one of a metal or asintered ceramic.
 15. The article of claim 13, wherein the plasmaresistant ceramic coating comprises at least one of Y₃Al₅O₁₂, Y₄Al₂O₉,Er₂O₃, Gd₂O₃, Y₂O₃, Er₃Al₅O₁₂, Gd₃Al₅O₁₂, YF₃, or Nd₂O₃.
 16. The ceramicarticle of claim 13, wherein the plasma resistant coating comprises aceramic compound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.17. A chamber component for a plasma etch reactor, the chamber componenthaving a plasma resistant ceramic coating on at least one surface, theplasma resistant ceramic coating having been formed by a processcomprising: feeding a ceramic powder into an atmospheric pressure plasmaspraying system at a powder feed rate; depositing a plasma resistantceramic coating on at least one surface of an article in a plasma sprayprocess by the atmospheric pressure plasma spraying system; andperforming an in-situ plasma flame heat treatment of the plasmaresistant ceramic coating by the atmospheric pressure plasma sprayingsystem to form a crust on the plasma resistant ceramic coating.
 18. Thechamber component of claim 17, wherein performing the in-situ plasmaflame heat treatment comprises: adjusting at least one of a plasmapower, a gun moving speed or a gun distance of the plasma sprayingsystem; and reducing the powder feed rate of the ceramic powder to zero.19. The chamber component of claim 17, wherein the plasma resistantceramic coating has a porosity of 1-5% and a thickness of at least 100microns, and wherein the crust has a lower porosity than the plasmaresistant ceramic coating and a thickness of less than about 50 microns.20. The chamber component of claim 17, the in-situ plasma flame heattreatment having been performed for approximately 0.5-20 minutes.